swap - 2 HDs

[Lars Kristiansen]

> Will Maier wrote:
>
>>On Fri, Dec 16, 2005 at 09:33:57AM -0300, Aguiar Magalhaes wrote:
>>
>>
>>>Is It recommended to configure  swap area in both HDs ??
>>>
>>>
>>
>>I don't see the point -- swap is where pages that don't fit in your
>>real memory go. It's less optimal than real memory in terms of
>>latency, but I don't see how two disks would make swap performance
>>much better.
>>
>>
> This is contrary to the "usual" advice which is to split swap across
> disks AFAIK.  I've never done any benchmarks, but my gut feeling would
> be that if the disks were on separate controllers, and if the machine
> did swap regularly then two swap partitions would be beneficial.  Even
> on the same controller it could easily make a difference since
> individual IDE/SATA disks can't actually reach the performance of the
> channel as a whole.

>From observation one can see that freebsd use the swap-partitions equally.
You probarly do want to make swap-partitions on all disks, but you may
later want to swapoff what is on the most busy disk if the disks are
unequally busy.

--
Lars

>
> Given that these are large hard disks, what's 2 or 4Gb in the grand
> scheme?  A drop in the ocean, so I would (and do) put swap on both.
>
> Of course, if the machine actually swaps regularly then investing in
> more RAM would give the best performance!
>
> --Alex
>
> PS If the two disks are larger than your actual needs, then you might
> want to consider emergency scenarios like one of your disks dieing.  If,
> for example, you put a spare, bootable version of FreeBSD on the 2nd
> disk to aid recovery then that OS will need a swap partition anyway and
> you might as well use it regularly.  $0.02
>
> _______________________________________________
> freebsd-questions at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> To unsubscribe, send any mail to
> "freebsd-questions-unsubscribe at freebsd.org"
>